180 PRACTICAL COURSE IN BOTANY 
Observe both branches in their natural position; what part 
of the leaf is turned upward, the edge or the surface of the 
blade? Change the position of the two sprigs, placing the 
vertically growing one horizontal, and the horizontal one 
vertical. What part of the leaves is turned upward in each? 
Fics. 232, 233. — Adjustment of leaves to different positions : 
232, upright ; 233, procumbent. 
197. Leaf mosaics. — Trees with horizontal or drooping 
branches, like the elm and beech, and vines growing along 
walls or trailing on the ground, generally display their foliage 
in flat, spreading layers, each leaf fit- 
ting in between the interstices of the 
others like the stones in a mosaic, 
whence this has been called the mosaic 
arrangement. (Plate 10.) In plants of 
more upright or bunchy habit, the 
leaves are placed at all angles, giving 
the appearance of a rosette when viewed 
from above, whence this is called the 
rosette arrangement. 
A variety of the same disposition is 
seen in the pyramidal shape assumed 
by plants with large, undivided leaves 
like the mullein and burdock (Fig. 237), in which access of 
light is secured by a mutual adjustment between the size 
and position of leaves, the upper ones becoming successively 
smaller. 
Fic. 234.— Leaf mosaic 
of elm. 
